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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
92 TS Appropriate touchscreen support is enabled.
93 USB USB support is enabled.
94 USBHID USB Human Interface Device support is enabled.
95 V4L Video For Linux support is enabled.
96 VGA The VGA console has been enabled.
97 VT Virtual terminal support is enabled.
98 WDT Watchdog support is enabled.
99 XT IBM PC/XT MFM hard disk support is enabled.
100 X86-32 X86-32, aka i386 architecture is enabled.
101 X86-64 X86-64 architecture is enabled.
102 More X86-64 boot options can be found in
103 Documentation/x86_64/boot-options.txt .
104 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
106 In addition, the following text indicates that the option:
108 BUGS= Relates to possible processor bugs on the said processor.
109 KNL Is a kernel start-up parameter.
110 BOOT Is a boot loader parameter.
112 Parameters denoted with BOOT are actually interpreted by the boot
113 loader, and have no meaning to the kernel directly.
114 Do not modify the syntax of boot loader parameters without extreme
115 need or coordination with <Documentation/i386/boot.txt>.
117 There are also arch-specific kernel-parameters not documented here.
118 See for example <Documentation/x86_64/boot-options.txt>.
120 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
121 a trailing = on the name of any parameter states that that parameter will
122 be entered as an environment variable, whereas its absence indicates that
123 it will appear as a kernel argument readable via /proc/cmdline by programs
124 running once the system is up.
126 The number of kernel parameters is not limited, but the length of the
127 complete command line (parameters including spaces etc.) is limited to
128 a fixed number of characters. This limit depends on the architecture
129 and is between 256 and 4096 characters. It is defined in the file
130 ./include/asm/setup.h as COMMAND_LINE_SIZE.
133 acpi= [HW,ACPI,X86-64,i386]
134 Advanced Configuration and Power Interface
135 Format: { force | off | ht | strict | noirq }
136 force -- enable ACPI if default was off
137 off -- disable ACPI if default was on
138 noirq -- do not use ACPI for IRQ routing
139 ht -- run only enough ACPI to enable Hyper Threading
140 strict -- Be less tolerant of platforms that are not
141 strictly ACPI specification compliant.
143 See also Documentation/power/pm.txt, pci=noacpi
145 acpi_apic_instance= [ACPI, IOAPIC]
146 Format: <int>
147 2: use 2nd APIC table, if available
148 1,0: use 1st APIC table
149 default: 0
151 acpi_sleep= [HW,ACPI] Sleep options
152 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
153 See Documentation/power/video.txt for s3_bios and s3_mode.
154 s3_beep is for debugging; it makes the PC's speaker beep
155 as soon as the kernel's real-mode entry point is called.
156 s4_nohwsig prevents ACPI hardware signature from being
157 used during resume from hibernation.
158 old_ordering causes the ACPI 1.0 ordering of the _PTS
159 control method, wrt putting devices into low power
160 states, to be enforced (the ACPI 2.0 ordering of _PTS is
161 used by default).
163 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
164 Format: { level | edge | high | low }
166 acpi_irq_balance [HW,ACPI]
167 ACPI will balance active IRQs
168 default in APIC mode
170 acpi_irq_nobalance [HW,ACPI]
171 ACPI will not move active IRQs (default)
172 default in PIC mode
174 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
175 use by PCI
176 Format: <irq>,<irq>...
178 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
179 Format: <irq>,<irq>...
181 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
183 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
184 Format: To spoof as Windows 98: ="Microsoft Windows"
186 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
187 acpi_osi="string1" # add string1 -- only one string
188 acpi_osi="!string2" # remove built-in string2
189 acpi_osi= # disable all strings
191 acpi_serialize [HW,ACPI] force serialization of AML methods
193 acpi_skip_timer_override [HW,ACPI]
194 Recognize and ignore IRQ0/pin2 Interrupt Override.
195 For broken nForce2 BIOS resulting in XT-PIC timer.
196 acpi_use_timer_override [HW,ACPI}
197 Use timer override. For some broken Nvidia NF5 boards
198 that require a timer override, but don't have
199 HPET
201 acpi.debug_layer= [HW,ACPI]
202 Format: <int>
203 Each bit of the <int> indicates an ACPI debug layer,
204 1: enable, 0: disable. It is useful for boot time
205 debugging. After system has booted up, it can be set
206 via /sys/module/acpi/parameters/debug_layer.
207 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
208 Available bits (add the numbers together) to enable debug output
209 for specific parts of the ACPI subsystem:
210 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
211 0x10 namespace 0x20 parser 0x40 dispatcher
212 0x80 executer 0x100 resources 0x200 acpica debugger
213 0x400 os services 0x800 acpica disassembler.
214 The number can be in decimal or prefixed with 0x in hex.
215 Warning: Many of these options can produce a lot of
216 output and make your system unusable. Be very careful.
218 acpi.debug_level= [HW,ACPI]
219 Format: <int>
220 Each bit of the <int> indicates an ACPI debug level,
221 which corresponds to the level in an ACPI_DEBUG_PRINT
222 statement. After system has booted up, this mask
223 can be set via /sys/module/acpi/parameters/debug_level.
225 CONFIG_ACPI_DEBUG must be enabled for this to produce
226 any output. The number can be in decimal or prefixed
227 with 0x in hex. Some of these options produce so much
228 output that the system is unusable.
230 The following global components are defined by the
231 ACPI CA:
232 0x01 error
233 0x02 warn
234 0x04 init
235 0x08 debug object
236 0x10 info
237 0x20 init names
238 0x40 parse
239 0x80 load
240 0x100 dispatch
241 0x200 execute
242 0x400 names
243 0x800 operation region
244 0x1000 bfield
245 0x2000 tables
246 0x4000 values
247 0x8000 objects
248 0x10000 resources
249 0x20000 user requests
250 0x40000 package
251 The number can be in decimal or prefixed with 0x in hex.
252 Warning: Many of these options can produce a lot of
253 output and make your system unusable. Be very careful.
255 acpi.power_nocheck= [HW,ACPI]
256 Format: 1/0 enable/disable the check of power state.
257 On some bogus BIOS the _PSC object/_STA object of
258 power resource can't return the correct device power
259 state. In such case it is unneccessary to check its
260 power state again in power transition.
261 1 : disable the power state check
263 acpi_pm_good [X86-32,X86-64]
264 Override the pmtimer bug detection: force the kernel
265 to assume that this machine's pmtimer latches its value
266 and always returns good values.
268 agp= [AGP]
269 { off | try_unsupported }
270 off: disable AGP support
271 try_unsupported: try to drive unsupported chipsets
272 (may crash computer or cause data corruption)
274 enable_timer_pin_1 [i386,x86-64]
275 Enable PIN 1 of APIC timer
276 Can be useful to work around chipset bugs
277 (in particular on some ATI chipsets).
278 The kernel tries to set a reasonable default.
280 disable_timer_pin_1 [i386,x86-64]
281 Disable PIN 1 of APIC timer
282 Can be useful to work around chipset bugs.
284 ad1848= [HW,OSS]
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
297 aha152x= [HW,SCSI]
298 See Documentation/scsi/aha152x.txt.
300 aha1542= [HW,SCSI]
301 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
303 aic7xxx= [HW,SCSI]
304 See Documentation/scsi/aic7xxx.txt.
306 aic79xx= [HW,SCSI]
307 See Documentation/scsi/aic79xx.txt.
309 amd_iommu= [HW,X86-84]
310 Pass parameters to the AMD IOMMU driver in the system.
311 Possible values are:
312 isolate - enable device isolation (each device, as far
313 as possible, will get its own protection
314 domain)
315 fullflush - enable flushing of IO/TLB entries when
316 they are unmapped. Otherwise they are
317 flushed before they will be reused, which
318 is a lot of faster
320 amd_iommu_size= [HW,X86-64]
321 Define the size of the aperture for the AMD IOMMU
322 driver. Possible values are:
323 '32M', '64M' (default), '128M', '256M', '512M', '1G'
325 amijoy.map= [HW,JOY] Amiga joystick support
326 Map of devices attached to JOY0DAT and JOY1DAT
327 Format: <a>,<b>
328 See also Documentation/kernel/input/joystick.txt
330 analog.map= [HW,JOY] Analog joystick and gamepad support
331 Specifies type or capabilities of an analog joystick
332 connected to one of 16 gameports
333 Format: <type1>,<type2>,..<type16>
335 apc= [HW,SPARC]
336 Power management functions (SPARCstation-4/5 + deriv.)
337 Format: noidle
338 Disable APC CPU standby support. SPARCstation-Fox does
339 not play well with APC CPU idle - disable it if you have
340 APC and your system crashes randomly.
342 apic= [APIC,i386] Advanced Programmable Interrupt Controller
343 Change the output verbosity whilst booting
344 Format: { quiet (default) | verbose | debug }
345 Change the amount of debugging information output
346 when initialising the APIC and IO-APIC components.
348 apm= [APM] Advanced Power Management
349 See header of arch/x86/kernel/apm_32.c.
351 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
352 Format: <io>,<irq>,<nodeID>
354 ataflop= [HW,M68k]
356 atarimouse= [HW,MOUSE] Atari Mouse
358 atascsi= [HW,SCSI] Atari SCSI
360 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
361 EzKey and similar keyboards
363 atkbd.reset= [HW] Reset keyboard during initialization
365 atkbd.set= [HW] Select keyboard code set
366 Format: <int> (2 = AT (default), 3 = PS/2)
368 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
369 keyboards
371 atkbd.softraw= [HW] Choose between synthetic and real raw mode
372 Format: <bool> (0 = real, 1 = synthetic (default))
374 atkbd.softrepeat= [HW]
375 Use software keyboard repeat
377 autotest [IA64]
379 baycom_epp= [HW,AX25]
380 Format: <io>,<mode>
382 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
383 Format: <io>,<mode>
384 See header of drivers/net/hamradio/baycom_par.c.
386 baycom_ser_fdx= [HW,AX25]
387 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
388 Format: <io>,<irq>,<mode>[,<baud>]
389 See header of drivers/net/hamradio/baycom_ser_fdx.c.
391 baycom_ser_hdx= [HW,AX25]
392 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
393 Format: <io>,<irq>,<mode>
394 See header of drivers/net/hamradio/baycom_ser_hdx.c.
396 boot_delay= Milliseconds to delay each printk during boot.
397 Values larger than 10 seconds (10000) are changed to
398 no delay (0).
399 Format: integer
401 bootmem_debug [KNL] Enable bootmem allocator debug messages.
403 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
404 bttv.radio= Most important insmod options are available as
405 kernel args too.
406 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
407 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
409 BusLogic= [HW,SCSI]
410 See drivers/scsi/BusLogic.c, comment before function
411 BusLogic_ParseDriverOptions().
413 c101= [NET] Moxa C101 synchronous serial card
415 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
416 Sometimes CPU hardware bugs make them report the cache
417 size incorrectly. The kernel will attempt work arounds
418 to fix known problems, but for some CPUs it is not
419 possible to determine what the correct size should be.
420 This option provides an override for these situations.
422 security= [SECURITY] Choose a security module to enable at boot.
423 If this boot parameter is not specified, only the first
424 security module asking for security registration will be
425 loaded. An invalid security module name will be treated
426 as if no module has been chosen.
428 capability.disable=
429 [SECURITY] Disable capabilities. This would normally
430 be used only if an alternative security model is to be
431 configured. Potentially dangerous and should only be
432 used if you are entirely sure of the consequences.
434 ccw_timeout_log [S390]
435 See Documentation/s390/CommonIO for details.
437 cgroup_disable= [KNL] Disable a particular controller
438 Format: {name of the controller(s) to disable}
439 {Currently supported controllers - "memory"}
441 checkreqprot [SELINUX] Set initial checkreqprot flag value.
442 Format: { "0" | "1" }
443 See security/selinux/Kconfig help text.
444 0 -- check protection applied by kernel (includes
445 any implied execute protection).
446 1 -- check protection requested by application.
447 Default value is set via a kernel config option.
448 Value can be changed at runtime via
449 /selinux/checkreqprot.
451 cio_ignore= [S390]
452 See Documentation/s390/CommonIO for details.
454 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
455 [Deprecated]
456 Forces specified clocksource (if available) to be used
457 when calculating gettimeofday(). If specified
458 clocksource is not available, it defaults to PIT.
459 Format: { pit | tsc | cyclone | pmtmr }
461 clocksource= [GENERIC_TIME] Override the default clocksource
462 Format: <string>
463 Override the default clocksource and use the clocksource
464 with the name specified.
465 Some clocksource names to choose from, depending on
466 the platform:
467 [all] jiffies (this is the base, fallback clocksource)
468 [ACPI] acpi_pm
469 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
470 pxa_timer,timer3,32k_counter,timer0_1
471 [AVR32] avr32
472 [X86-32] pit,hpet,tsc,vmi-timer;
473 scx200_hrt on Geode; cyclone on IBM x440
474 [MIPS] MIPS
475 [PARISC] cr16
476 [S390] tod
477 [SH] SuperH
478 [SPARC64] tick
479 [X86-64] hpet,tsc
481 clearcpuid=BITNUM [X86]
482 Disable CPUID feature X for the kernel. See
483 include/asm-x86/cpufeature.h for the valid bit numbers.
484 Note the Linux specific bits are not necessarily
485 stable over kernel options, but the vendor specific
486 ones should be.
487 Also note that user programs calling CPUID directly
488 or using the feature without checking anything
489 will still see it. This just prevents it from
490 being used by the kernel or shown in /proc/cpuinfo.
491 Also note the kernel might malfunction if you disable
492 some critical bits.
494 code_bytes [IA32/X86_64] How many bytes of object code to print
495 in an oops report.
496 Range: 0 - 8192
497 Default: 64
499 hpet= [X86-32,HPET] option to control HPET usage
500 Format: { enable (default) | disable | force }
501 disable: disable HPET and use PIT instead
502 force: allow force enabled of undocumented chips (ICH4,
503 VIA, nVidia)
505 com20020= [HW,NET] ARCnet - COM20020 chipset
506 Format:
507 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
509 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 Format: <io>[,<irq>]
512 com90xx= [HW,NET]
513 ARCnet - COM90xx chipset (memory-mapped buffers)
514 Format: <io>[,<irq>[,<memstart>]]
516 condev= [HW,S390] console device
517 conmode=
519 console= [KNL] Output console device and options.
521 tty<n> Use the virtual console device <n>.
523 ttyS<n>[,options]
524 ttyUSB0[,options]
525 Use the specified serial port. The options are of
526 the form "bbbbpnf", where "bbbb" is the baud rate,
527 "p" is parity ("n", "o", or "e"), "n" is number of
528 bits, and "f" is flow control ("r" for RTS or
529 omit it). Default is "9600n8".
531 See Documentation/serial-console.txt for more
532 information. See
533 Documentation/networking/netconsole.txt for an
534 alternative.
536 uart[8250],io,<addr>[,options]
537 uart[8250],mmio,<addr>[,options]
538 Start an early, polled-mode console on the 8250/16550
539 UART at the specified I/O port or MMIO address,
540 switching to the matching ttyS device later. The
541 options are the same as for ttyS, above.
543 If the device connected to the port is not a TTY but a braille
544 device, prepend "brl," before the device type, for instance
545 console=brl,ttyS0
546 For now, only VisioBraille is supported.
548 earlycon= [KNL] Output early console device and options.
549 uart[8250],io,<addr>[,options]
550 uart[8250],mmio,<addr>[,options]
551 Start an early, polled-mode console on the 8250/16550
552 UART at the specified I/O port or MMIO address.
553 The options are the same as for ttyS, above.
555 no_console_suspend
556 [HW] Never suspend the console
557 Disable suspending of consoles during suspend and
558 hibernate operations. Once disabled, debugging
559 messages can reach various consoles while the rest
560 of the system is being put to sleep (ie, while
561 debugging driver suspend/resume hooks). This may
562 not work reliably with all consoles, but is known
563 to work with serial and VGA consoles.
565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
566 Format:
567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
569 crashkernel=nn[KMG]@ss[KMG]
570 [KNL] Reserve a chunk of physical memory to
571 hold a kernel to switch to with kexec on panic.
573 crashkernel=range1:size1[,range2:size2,...][@offset]
574 [KNL] Same as above, but depends on the memory
575 in the running system. The syntax of range is
576 start-[end] where start and end are both
577 a memory unit (amount[KMG]). See also
578 Documentation/kdump/kdump.txt for a example.
580 cs4232= [HW,OSS]
581 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
583 cs89x0_dma= [HW,NET]
584 Format: <dma>
586 cs89x0_media= [HW,NET]
587 Format: { rj45 | aui | bnc }
589 dasd= [HW,NET]
590 See header of drivers/s390/block/dasd_devmap.c.
592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
593 (one device per port)
594 Format: <port#>,<type>
595 See also Documentation/input/joystick-parport.txt
597 debug [KNL] Enable kernel debugging (events log level).
599 debug_locks_verbose=
600 [KNL] verbose self-tests
601 Format=<0|1>
602 Print debugging info while doing the locking API
603 self-tests.
604 We default to 0 (no extra messages), setting it to
605 1 will print _a lot_ more information - normally
606 only useful to kernel developers.
608 debug_objects [KNL] Enable object debugging
610 debugpat [X86] Enable PAT debugging
612 decnet.addr= [HW,NET]
613 Format: <area>[,<node>]
614 See also Documentation/networking/decnet.txt.
616 vt.default_blu= [VT]
617 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
618 Change the default blue palette of the console.
619 This is a 16-member array composed of values
620 ranging from 0-255.
622 vt.default_grn= [VT]
623 Format: <green0>,<green1>,<green2>,...,<green15>
624 Change the default green palette of the console.
625 This is a 16-member array composed of values
626 ranging from 0-255.
628 vt.default_red= [VT]
629 Format: <red0>,<red1>,<red2>,...,<red15>
630 Change the default red palette of the console.
631 This is a 16-member array composed of values
632 ranging from 0-255.
634 vt.default_utf8=
635 [VT]
636 Format=<0|1>
637 Set system-wide default UTF-8 mode for all tty's.
638 Default is 1, i.e. UTF-8 mode is enabled for all
639 newly opened terminals.
641 dhash_entries= [KNL]
642 Set number of hash buckets for dentry cache.
644 digi= [HW,SERIAL]
645 IO parameters + enable/disable command.
647 digiepca= [HW,SERIAL]
648 See drivers/char/README.epca and
649 Documentation/digiepca.txt.
651 disable_mtrr_cleanup [X86]
652 enable_mtrr_cleanup [X86]
653 The kernel tries to adjust MTRR layout from continuous
654 to discrete, to make X server driver able to add WB
655 entry later. This parameter enables/disables that.
657 mtrr_chunk_size=nn[KMG] [X86]
658 used for mtrr cleanup. It is largest continous chunk
659 that could hold holes aka. UC entries.
661 mtrr_gran_size=nn[KMG] [X86]
662 Used for mtrr cleanup. It is granularity of mtrr block.
663 Default is 1.
664 Large value could prevent small alignment from
665 using up MTRRs.
667 mtrr_spare_reg_nr=n [X86]
668 Format: <integer>
669 Range: 0,7 : spare reg number
670 Default : 1
671 Used for mtrr cleanup. It is spare mtrr entries number.
672 Set to 2 or more if your graphical card needs more.
674 disable_mtrr_trim [X86, Intel and AMD only]
675 By default the kernel will trim any uncacheable
676 memory out of your available memory pool based on
677 MTRR settings. This parameter disables that behavior,
678 possibly causing your machine to run very slowly.
680 dmasound= [HW,OSS] Sound subsystem buffers
682 dscc4.setup= [NET]
684 dtc3181e= [HW,SCSI]
686 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
687 earlyprintk=vga
688 earlyprintk=serial[,ttySn[,baudrate]]
689 earlyprintk=dbgp
691 Append ",keep" to not disable it when the real console
692 takes over.
694 Only vga or serial or usb debug port at a time.
696 Currently only ttyS0 and ttyS1 are supported.
698 Interaction with the standard serial driver is not
699 very good.
701 The VGA output is eventually overwritten by the real
702 console.
704 eata= [HW,SCSI]
706 edd= [EDD]
707 Format: {"off" | "on" | "skip[mbr]"}
709 eisa_irq_edge= [PARISC,HW]
710 See header of drivers/parisc/eisa.c.
712 elanfreq= [X86-32]
713 See comment before function elanfreq_setup() in
714 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
716 elevator= [IOSCHED]
717 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
718 See Documentation/block/as-iosched.txt and
719 Documentation/block/deadline-iosched.txt for details.
721 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
722 Specifies physical address of start of kernel core
723 image elf header. Generally kexec loader will
724 pass this option to capture kernel.
725 See Documentation/kdump/kdump.txt for details.
727 enforcing [SELINUX] Set initial enforcing status.
728 Format: {"0" | "1"}
729 See security/selinux/Kconfig help text.
730 0 -- permissive (log only, no denials).
731 1 -- enforcing (deny and log).
732 Default value is 0.
733 Value can be changed at runtime via /selinux/enforce.
735 es1371= [HW,OSS]
736 Format: <spdif>,[<nomix>,[<amplifier>]]
737 See also header of sound/oss/es1371.c.
739 ether= [HW,NET] Ethernet cards parameters
740 This option is obsoleted by the "netdev=" option, which
741 has equivalent usage. See its documentation for details.
743 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
744 Format: <io>[,<irq>]
746 failslab=
747 fail_page_alloc=
748 fail_make_request=[KNL]
749 General fault injection mechanism.
750 Format: <interval>,<probability>,<space>,<times>
751 See also /Documentation/fault-injection/.
753 fd_mcs= [HW,SCSI]
754 See header of drivers/scsi/fd_mcs.c.
756 fdomain= [HW,SCSI]
757 See header of drivers/scsi/fdomain.c.
759 floppy= [HW]
760 See Documentation/floppy.txt.
762 force_pal_cache_flush
763 [IA-64] Avoid check_sal_cache_flush which may hang on
764 buggy SAL_CACHE_FLUSH implementations. Using this
765 parameter will force ia64_sal_cache_flush to call
766 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
768 gamecon.map[2|3]=
769 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
770 support via parallel port (up to 5 devices per port)
771 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
772 See also Documentation/input/joystick-parport.txt
774 gamma= [HW,DRM]
776 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
777 Format: off | on
778 default: on
780 gdth= [HW,SCSI]
781 See header of drivers/scsi/gdth.c.
783 gpt [EFI] Forces disk with valid GPT signature but
784 invalid Protective MBR to be treated as GPT.
786 gvp11= [HW,SCSI]
788 hashdist= [KNL,NUMA] Large hashes allocated during boot
789 are distributed across NUMA nodes. Defaults on
790 for IA-64, off otherwise.
791 Format: 0 | 1 (for off | on)
793 hcl= [IA-64] SGI's Hardware Graph compatibility layer
795 hd= [EIDE] (E)IDE hard drive subsystem geometry
796 Format: <cyl>,<head>,<sect>
798 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
799 size of <nn>. This works even on boxes that have no
800 highmem otherwise. This also works to reduce highmem
801 size on bigger boxes.
803 highres= [KNL] Enable/disable high resolution timer mode.
804 Valid parameters: "on", "off"
805 Default: "on"
807 hisax= [HW,ISDN]
808 See Documentation/isdn/README.HiSax.
810 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
811 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
812 On x86-64 and powerpc, this option can be specified
813 multiple times interleaved with hugepages= to reserve
814 huge pages of different sizes. Valid pages sizes on
815 x86-64 are 2M (when the CPU supports "pse") and 1G
816 (when the CPU supports the "pdpe1gb" cpuinfo flag)
817 Note that 1GB pages can only be allocated at boot time
818 using hugepages= and not freed afterwards.
819 default_hugepagesz=
820 [same as hugepagesz=] The size of the default
821 HugeTLB page size. This is the size represented by
822 the legacy /proc/ hugepages APIs, used for SHM, and
823 default size when mounting hugetlbfs filesystems.
824 Defaults to the default architecture's huge page size
825 if not specified.
827 hlt [BUGS=ARM,SH]
829 i8042.debug [HW] Toggle i8042 debug mode
830 i8042.direct [HW] Put keyboard port into non-translated mode
831 i8042.dumbkbd [HW] Pretend that controller can only read data from
832 keyboard and cannot control its state
833 (Don't attempt to blink the leds)
834 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
835 i8042.nokbd [HW] Don't check/create keyboard port
836 i8042.noloop [HW] Disable the AUX Loopback command while probing
837 for the AUX port
838 i8042.nomux [HW] Don't check presence of an active multiplexing
839 controller
840 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
841 controllers
842 i8042.panicblink=
843 [HW] Frequency with which keyboard LEDs should blink
844 when kernel panics (default is 0.5 sec)
845 i8042.reset [HW] Reset the controller during init and cleanup
846 i8042.unlock [HW] Unlock (ignore) the keylock
848 i810= [HW,DRM]
850 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
851 indicates that the driver is running on unsupported
852 hardware.
853 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
854 does not match list of supported models.
855 i8k.power_status
856 [HW] Report power status in /proc/i8k
857 (disabled by default)
858 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
859 capability is set.
861 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
862 See Documentation/mca.txt.
864 icn= [HW,ISDN]
865 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
867 ide= [HW] (E)IDE subsystem
868 Format: ide=nodma or ide=doubler
869 See Documentation/ide/ide.txt.
871 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
872 See Documentation/ide/ide.txt.
874 idle= [X86]
875 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
876 Poll forces a polling idle loop that can slightly improves the performance
877 of waking up a idle CPU, but will use a lot of power and make the system
878 run hot. Not recommended.
879 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
880 to not use it because it doesn't save as much power as a normal idle
881 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
882 as idle=poll.
883 idle=halt. Halt is forced to be used for CPU idle.
884 In such case C2/C3 won't be used again.
885 idle=nomwait. Disable mwait for CPU C-states
887 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
888 Claim all unknown PCI IDE storage controllers.
890 ignore_loglevel [KNL]
891 Ignore loglevel setting - this will print /all/
892 kernel messages to the console. Useful for debugging.
894 ihash_entries= [KNL]
895 Set number of hash buckets for inode cache.
897 in2000= [HW,SCSI]
898 See header of drivers/scsi/in2000.c.
900 init= [KNL]
901 Format: <full_path>
902 Run specified binary instead of /sbin/init as init
903 process.
905 initcall_debug [KNL] Trace initcalls as they are executed. Useful
906 for working out where the kernel is dying during
907 startup.
909 initrd= [BOOT] Specify the location of the initial ramdisk
911 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
912 Format: <irq>
914 inttest= [IA64]
916 iommu= [x86]
917 off
918 force
919 noforce
920 biomerge
921 panic
922 nopanic
923 merge
924 nomerge
925 forcesac
926 soft
929 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
930 off
931 Disable intel iommu driver.
932 igfx_off [Default Off]
933 By default, gfx is mapped as normal device. If a gfx
934 device has a dedicated DMAR unit, the DMAR unit is
935 bypassed by not enabling DMAR with this option. In
936 this case, gfx device will use physical address for
937 DMA.
938 forcedac [x86_64]
939 With this option iommu will not optimize to look
940 for io virtual address below 32 bit forcing dual
941 address cycle on pci bus for cards supporting greater
942 than 32 bit addressing. The default is to look
943 for translation below 32 bit and if not available
944 then look in the higher range.
945 strict [Default Off]
946 With this option on every unmap_single operation will
947 result in a hardware IOTLB flush operation as opposed
948 to batching them for performance.
950 io_delay= [X86-32,X86-64] I/O delay method
951 0x80
952 Standard port 0x80 based delay
953 0xed
954 Alternate port 0xed based delay (needed on some systems)
955 udelay
956 Simple two microseconds delay
957 none
958 No delay
960 io7= [HW] IO7 for Marvel based alpha systems
961 See comment before marvel_specify_io7 in
962 arch/alpha/kernel/core_marvel.c.
964 ip= [IP_PNP]
965 See Documentation/filesystems/nfsroot.txt.
967 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
968 See comment before ip2_setup() in
969 drivers/char/ip2/ip2base.c.
971 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
972 See header of drivers/scsi/ips.c.
974 ports= [IP_VS_FTP] IPVS ftp helper module
975 Default is 21.
976 Up to 8 (IP_VS_APP_MAX_PORTS) ports
977 may be specified.
978 Format: <port>,<port>....
980 irqfixup [HW]
981 When an interrupt is not handled search all handlers
982 for it. Intended to get systems with badly broken
983 firmware running.
985 irqpoll [HW]
986 When an interrupt is not handled search all handlers
987 for it. Also check all handlers each timer
988 interrupt. Intended to get systems with badly broken
989 firmware running.
991 isapnp= [ISAPNP]
992 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
994 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
995 Format:
996 <cpu number>,...,<cpu number>
997 or
998 <cpu number>-<cpu number> (must be a positive range in ascending order)
999 or a mixture
1000 <cpu number>,...,<cpu number>-<cpu number>
1001 This option can be used to specify one or more CPUs
1002 to isolate from the general SMP balancing and scheduling
1003 algorithms. The only way to move a process onto or off
1004 an "isolated" CPU is via the CPU affinity syscalls.
1005 <cpu number> begins at 0 and the maximum value is
1006 "number of CPUs in system - 1".
1008 This option is the preferred way to isolate CPUs. The
1009 alternative -- manually setting the CPU mask of all
1010 tasks in the system -- can cause problems and
1011 suboptimal load balancer performance.
1013 iucv= [HW,NET]
1015 js= [HW,JOY] Analog joystick
1016 See Documentation/input/joystick.txt.
1018 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1019 specifies the amount of memory usable by the kernel
1020 for non-movable allocations. The requested amount is
1021 spread evenly throughout all nodes in the system. The
1022 remaining memory in each node is used for Movable
1023 pages. In the event, a node is too small to have both
1024 kernelcore and Movable pages, kernelcore pages will
1025 take priority and other nodes will have a larger number
1026 of kernelcore pages. The Movable zone is used for the
1027 allocation of pages that may be reclaimed or moved
1028 by the page migration subsystem. This means that
1029 HugeTLB pages may not be allocated from this zone.
1030 Note that allocations like PTEs-from-HighMem still
1031 use the HighMem zone if it exists, and the Normal
1032 zone if it does not.
1034 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1035 is similar to kernelcore except it specifies the
1036 amount of memory used for migratable allocations.
1037 If both kernelcore and movablecore is specified,
1038 then kernelcore will be at *least* the specified
1039 value but may be more. If movablecore on its own
1040 is specified, the administrator must be careful
1041 that the amount of memory usable for all allocations
1042 is not too small.
1044 keepinitrd [HW,ARM]
1046 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1047 in oops dumps.
1049 kgdboc= [HW] kgdb over consoles.
1050 Requires a tty driver that supports console polling.
1051 (only serial suported for now)
1052 Format: <serial_device>[,baud]
1054 kmac= [MIPS] korina ethernet MAC address.
1055 Configure the RouterBoard 532 series on-chip
1056 Ethernet adapter MAC address.
1058 l2cr= [PPC]
1060 l3cr= [PPC]
1062 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1063 disabled it.
1065 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1066 C2 power state.
1068 libata.dma= [LIBATA] DMA control
1069 libata.dma=0 Disable all PATA and SATA DMA
1070 libata.dma=1 PATA and SATA Disk DMA only
1071 libata.dma=2 ATAPI (CDROM) DMA only
1072 libata.dma=4 Compact Flash DMA only
1073 Combinations also work, so libata.dma=3 enables DMA
1074 for disks and CDROMs, but not CFs.
1076 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1077 when set.
1078 Format: <int>
1080 libata.force= [LIBATA] Force configurations. The format is comma
1081 separated list of "[ID:]VAL" where ID is
1082 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1083 matching port, link or device. Basically, it matches
1084 the ATA ID string printed on console by libata. If
1085 the whole ID part is omitted, the last PORT and DEVICE
1086 values are used. If ID hasn't been specified yet, the
1087 configuration applies to all ports, links and devices.
1089 If only DEVICE is omitted, the parameter applies to
1090 the port and all links and devices behind it. DEVICE
1091 number of 0 either selects the first device or the
1092 first fan-out link behind PMP device. It does not
1093 select the host link. DEVICE number of 15 selects the
1094 host link and device attached to it.
1096 The VAL specifies the configuration to force. As long
1097 as there's no ambiguity shortcut notation is allowed.
1098 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1099 The following configurations can be forced.
1101 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1102 Any ID with matching PORT is used.
1104 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1106 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1107 udma[/][16,25,33,44,66,100,133] notation is also
1108 allowed.
1110 * [no]ncq: Turn on or off NCQ.
1112 * nohrst, nosrst, norst: suppress hard, soft
1113 and both resets.
1115 If there are multiple matching configurations changing
1116 the same attribute, the last one is used.
1118 load_ramdisk= [RAM] List of ramdisks to load from floppy
1119 See Documentation/ramdisk.txt.
1121 lockd.nlm_grace_period=P [NFS] Assign grace period.
1122 Format: <integer>
1124 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1125 Format: <integer>
1127 lockd.nlm_timeout=T [NFS] Assign timeout value.
1128 Format: <integer>
1130 lockd.nlm_udpport=M [NFS] Assign UDP port.
1131 Format: <integer>
1133 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1134 Format: <irq>
1136 loglevel= All Kernel Messages with a loglevel smaller than the
1137 console loglevel will be printed to the console. It can
1138 also be changed with klogd or other programs. The
1139 loglevels are defined as follows:
1141 0 (KERN_EMERG) system is unusable
1142 1 (KERN_ALERT) action must be taken immediately
1143 2 (KERN_CRIT) critical conditions
1144 3 (KERN_ERR) error conditions
1145 4 (KERN_WARNING) warning conditions
1146 5 (KERN_NOTICE) normal but significant condition
1147 6 (KERN_INFO) informational
1148 7 (KERN_DEBUG) debug-level messages
1150 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1151 Format: { n | nk | nM }
1152 n must be a power of two. The default size
1153 is set in the kernel config file.
1155 logo.nologo [FB] Disables display of the built-in Linux logo.
1156 This may be used to provide more screen space for
1157 kernel log messages and is useful when debugging
1158 kernel boot problems.
1160 lp=0 [LP] Specify parallel ports to use, e.g,
1161 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1162 lp=reset first parallel port). 'lp=0' disables the
1163 lp=auto printer driver. 'lp=reset' (which can be
1164 specified in addition to the ports) causes
1165 attached printers to be reset. Using
1166 lp=port1,port2,... specifies the parallel ports
1167 to associate lp devices with, starting with
1168 lp0. A port specification may be 'none' to skip
1169 that lp device, or a parport name such as
1170 'parport0'. Specifying 'lp=auto' instead of a
1171 port specification list means that device IDs
1172 from each port should be examined, to see if
1173 an IEEE 1284-compliant printer is attached; if
1174 so, the driver will manage that printer.
1175 See also header of drivers/char/lp.c.
1177 lpj=n [KNL]
1178 Sets loops_per_jiffy to given constant, thus avoiding
1179 time-consuming boot-time autodetection (up to 250 ms per
1180 CPU). 0 enables autodetection (default). To determine
1181 the correct value for your kernel, boot with normal
1182 autodetection and see what value is printed. Note that
1183 on SMP systems the preset will be applied to all CPUs,
1184 which is likely to cause problems if your CPUs need
1185 significantly divergent settings. An incorrect value
1186 will cause delays in the kernel to be wrong, leading to
1187 unpredictable I/O errors and other breakage. Although
1188 unlikely, in the extreme case this might damage your
1189 hardware.
1191 ltpc= [NET]
1192 Format: <io>,<irq>,<dma>
1194 mac5380= [HW,SCSI] Format:
1195 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1197 machvec= [IA64] Force the use of a particular machine-vector
1198 (machvec) in a generic kernel.
1199 Example: machvec=hpzx1_swiotlb
1201 max_loop= [LOOP] Maximum number of loopback devices that can
1202 be mounted
1203 Format: <1-256>
1205 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1206 should make use of. maxcpus=n : n >= 0 limits the
1207 kernel to using 'n' processors. n=0 is a special case,
1208 it is equivalent to "nosmp", which also disables
1209 the IO APIC.
1211 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1212 equal to this physical address is ignored.
1214 max_luns= [SCSI] Maximum number of LUNs to probe.
1215 Should be between 1 and 2^32-1.
1217 max_report_luns=
1218 [SCSI] Maximum number of LUNs received.
1219 Should be between 1 and 16384.
1221 mcatest= [IA-64]
1223 mce [X86-32] Machine Check Exception
1225 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1227 md= [HW] RAID subsystems devices and level
1228 See Documentation/md.txt.
1230 mdacon= [MDA]
1231 Format: <first>,<last>
1232 Specifies range of consoles to be captured by the MDA.
1234 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1235 Amount of memory to be used when the kernel is not able
1236 to see the whole system memory or for test.
1237 [X86-32] Use together with memmap= to avoid physical
1238 address space collisions. Without memmap= PCI devices
1239 could be placed at addresses belonging to unused RAM.
1241 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1242 memory.
1244 memchunk=nn[KMG]
1245 [KNL,SH] Allow user to override the default size for
1246 per-device physically contiguous DMA buffers.
1248 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1249 E820 memory map, as specified by the user.
1250 Such memmap=exactmap lines can be constructed based on
1251 BIOS output or other requirements. See the memmap=nn@ss
1252 option description.
1254 memmap=nn[KMG]@ss[KMG]
1255 [KNL] Force usage of a specific region of memory
1256 Region of memory to be used, from ss to ss+nn.
1258 memmap=nn[KMG]#ss[KMG]
1259 [KNL,ACPI] Mark specific memory as ACPI data.
1260 Region of memory to be used, from ss to ss+nn.
1262 memmap=nn[KMG]$ss[KMG]
1263 [KNL,ACPI] Mark specific memory as reserved.
1264 Region of memory to be used, from ss to ss+nn.
1265 Example: Exclude memory from 0x18690000-0x1869ffff
1266 memmap=64K$0x18690000
1267 or
1268 memmap=0x10000$0x18690000
1270 memory_corruption_check=0/1 [X86]
1271 Some BIOSes seem to corrupt the first 64k of
1272 memory when doing things like suspend/resume.
1273 Setting this option will scan the memory
1274 looking for corruption. Enabling this will
1275 both detect corruption and prevent the kernel
1276 from using the memory being corrupted.
1277 However, its intended as a diagnostic tool; if
1278 repeatable BIOS-originated corruption always
1279 affects the same memory, you can use memmap=
1280 to prevent the kernel from using that memory.
1282 memory_corruption_check_size=size [X86]
1283 By default it checks for corruption in the low
1284 64k, making this memory unavailable for normal
1285 use. Use this parameter to scan for
1286 corruption in more or less memory.
1288 memory_corruption_check_period=seconds [X86]
1289 By default it checks for corruption every 60
1290 seconds. Use this parameter to check at some
1291 other rate. 0 disables periodic checking.
1293 memtest= [KNL,X86] Enable memtest
1294 Format: <integer>
1295 range: 0,4 : pattern number
1296 default : 0 <disable>
1298 meye.*= [HW] Set MotionEye Camera parameters
1299 See Documentation/video4linux/meye.txt.
1301 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1302 Multi-Function General Purpose Timers on AMD Geode
1303 platforms.
1305 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1306 the BIOS has incorrectly applied a workaround. TinyBIOS
1307 version 0.98 is known to be affected, 0.99 fixes the
1308 problem by letting the user disable the workaround.
1310 mga= [HW,DRM]
1312 mminit_loglevel=
1313 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1314 parameter allows control of the logging verbosity for
1315 the additional memory initialisation checks. A value
1316 of 0 disables mminit logging and a level of 4 will
1317 log everything. Information is printed at KERN_DEBUG
1318 so loglevel=8 may also need to be specified.
1320 mousedev.tap_time=
1321 [MOUSE] Maximum time between finger touching and
1322 leaving touchpad surface for touch to be considered
1323 a tap and be reported as a left button click (for
1324 touchpads working in absolute mode only).
1325 Format: <msecs>
1326 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1327 reporting absolute coordinates, such as tablets
1328 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1329 reporting absolute coordinates, such as tablets
1331 mpu401= [HW,OSS]
1332 Format: <io>,<irq>
1334 MTD_Partition= [MTD]
1335 Format: <name>,<region-number>,<size>,<offset>
1337 MTD_Region= [MTD] Format:
1338 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1340 mtdparts= [MTD]
1341 See drivers/mtd/cmdlinepart.c.
1343 mtdset= [ARM]
1344 ARM/S3C2412 JIVE boot control
1346 See arch/arm/mach-s3c2412/mach-jive.c
1348 mtouchusb.raw_coordinates=
1349 [HW] Make the MicroTouch USB driver use raw coordinates
1350 ('y', default) or cooked coordinates ('n')
1352 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1354 NCR_D700= [HW,SCSI]
1355 See header of drivers/scsi/NCR_D700.c.
1357 ncr5380= [HW,SCSI]
1359 ncr53c400= [HW,SCSI]
1361 ncr53c400a= [HW,SCSI]
1363 ncr53c406a= [HW,SCSI]
1365 ncr53c8xx= [HW,SCSI]
1367 netdev= [NET] Network devices parameters
1368 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1369 Note that mem_start is often overloaded to mean
1370 something different and driver-specific.
1371 This usage is only documented in each driver source
1372 file if at all.
1374 nf_conntrack.acct=
1375 [NETFILTER] Enable connection tracking flow accounting
1376 0 to disable accounting
1377 1 to enable accounting
1378 Default value depends on CONFIG_NF_CT_ACCT that is
1379 going to be removed in 2.6.29.
1381 nfsaddrs= [NFS]
1382 See Documentation/filesystems/nfsroot.txt.
1384 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1385 See Documentation/filesystems/nfsroot.txt.
1387 nfs.callback_tcpport=
1388 [NFS] set the TCP port on which the NFSv4 callback
1389 channel should listen.
1391 nfs.idmap_cache_timeout=
1392 [NFS] set the maximum lifetime for idmapper cache
1393 entries.
1395 nfs.enable_ino64=
1396 [NFS] enable 64-bit inode numbers.
1397 If zero, the NFS client will fake up a 32-bit inode
1398 number for the readdir() and stat() syscalls instead
1399 of returning the full 64-bit number.
1400 The default is to return 64-bit inode numbers.
1402 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1403 when a NMI is triggered.
1404 Format: [state][,regs][,debounce][,die]
1406 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1408 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1409 emulation library even if a 387 maths coprocessor
1410 is present.
1412 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1413 caches in the slab allocator. Saves per-node memory,
1414 but will impact performance.
1416 noalign [KNL,ARM]
1418 noapic [SMP,APIC] Tells the kernel to not make use of any
1419 IOAPICs that may be present in the system.
1421 nobats [PPC] Do not use BATs for mapping kernel lowmem
1422 on "Classic" PPC cores.
1424 nocache [ARM]
1426 nodelayacct [KNL] Disable per-task delay accounting
1428 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1430 nodsp [SH] Disable hardware DSP at boot time.
1432 noefi [X86-32,X86-64] Disable EFI runtime services support.
1434 noexec [IA-64]
1436 noexec [X86-32,X86-64]
1437 On X86-32 available only on PAE configured kernels.
1438 noexec=on: enable non-executable mappings (default)
1439 noexec=off: disable non-executable mappings
1441 noexec32 [X86-64]
1442 This affects only 32-bit executables.
1443 noexec32=on: enable non-executable mappings (default)
1444 read doesn't imply executable mappings
1445 noexec32=off: disable non-executable mappings
1446 read implies executable mappings
1448 nofpu [SH] Disable hardware FPU at boot time.
1450 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1451 register save and restore. The kernel will only save
1452 legacy floating-point registers on task switch.
1454 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1456 nohlt [BUGS=ARM,SH]
1458 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1459 instruction doesn't work correctly and not to
1460 use it.
1462 nohalt [IA-64] Tells the kernel not to use the power saving
1463 function PAL_HALT_LIGHT when idle. This increases
1464 power-consumption. On the positive side, it reduces
1465 interrupt wake-up latency, which may improve performance
1466 in certain environments such as networked servers or
1467 real-time systems.
1469 nohz= [KNL] Boottime enable/disable dynamic ticks
1470 Valid arguments: on, off
1471 Default: on
1473 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1475 noirqdebug [X86-32] Disables the code which attempts to detect and
1476 disable unhandled interrupt sources.
1478 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1479 broken timer IRQ sources.
1481 noisapnp [ISAPNP] Disables ISA PnP code.
1483 noinitrd [RAM] Tells the kernel not to load any configured
1484 initial RAM disk.
1486 nointroute [IA-64]
1488 nojitter [IA64] Disables jitter checking for ITC timers.
1490 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1492 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1494 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1496 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1497 default x2apic cluster mode on platforms
1498 supporting x2apic.
1500 noltlbs [PPC] Do not use large page/tlb entries for kernel
1501 lowmem mapping on PPC40x.
1503 nomca [IA-64] Disable machine check abort handling
1505 nomce [X86-32] Machine Check Exception
1507 nomfgpt [X86-32] Disable Multi-Function General Purpose
1508 Timer usage (for AMD Geode machines).
1510 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1512 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1513 with UP alternatives
1515 noresidual [PPC] Don't use residual data on PReP machines.
1517 noresume [SWSUSP] Disables resume and restores original swap
1518 space.
1520 no-scroll [VGA] Disables scrollback.
1521 This is required for the Braillex ib80-piezo Braille
1522 reader made by F.H. Papenmeier (Germany).
1524 nosbagart [IA-64]
1526 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1528 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1529 and disable the IO APIC. legacy for "maxcpus=0".
1531 nosoftlockup [KNL] Disable the soft-lockup detector.
1533 nosync [HW,M68K] Disables sync negotiation for all devices.
1535 notsc [BUGS=X86-32] Disable Time Stamp Counter
1537 nousb [USB] Disable the USB subsystem
1539 nowb [ARM]
1541 nptcg= [IA64] Override max number of concurrent global TLB
1542 purges which is reported from either PAL_VM_SUMMARY or
1543 SAL PALO.
1545 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1546 one of ['zone', 'node', 'default'] can be specified
1547 This can be set from sysctl after boot.
1548 See Documentation/sysctl/vm.txt for details.
1550 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1552 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1553 Rather than timing out after 20 ms if an EC
1554 command is not properly ACKed, override the length
1555 of the timeout. We have interrupts disabled while
1556 waiting for the ACK, so if this is set too high
1557 interrupts *may* be lost!
1559 opl3= [HW,OSS]
1560 Format: <io>
1562 oprofile.timer= [HW]
1563 Use timer interrupt instead of performance counters
1565 osst= [HW,SCSI] SCSI Tape Driver
1566 Format: <buffer_size>,<write_threshold>
1567 See also Documentation/scsi/st.txt.
1569 panic= [KNL] Kernel behaviour on panic
1570 Format: <timeout>
1572 parkbd.port= [HW] Parallel port number the keyboard adapter is
1573 connected to, default is 0.
1574 Format: <parport#>
1575 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1576 0 for XT, 1 for AT (default is AT).
1577 Format: <mode>
1579 parport= [HW,PPT] Specify parallel ports. 0 disables.
1580 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1581 Use 'auto' to force the driver to use any
1582 IRQ/DMA settings detected (the default is to
1583 ignore detected IRQ/DMA settings because of
1584 possible conflicts). You can specify the base
1585 address, IRQ, and DMA settings; IRQ and DMA
1586 should be numbers, or 'auto' (for using detected
1587 settings on that particular port), or 'nofifo'
1588 (to avoid using a FIFO even if it is detected).
1589 Parallel ports are assigned in the order they
1590 are specified on the command line, starting
1591 with parport0.
1593 parport_init_mode= [HW,PPT]
1594 Configure VIA parallel port to operate in
1595 a specific mode. This is necessary on Pegasos
1596 computer where firmware has no options for setting
1597 up parallel port mode and sets it to spp.
1598 Currently this function knows 686a and 8231 chips.
1599 Format: [spp|ps2|epp|ecp|ecpepp]
1601 pas2= [HW,OSS] Format:
1602 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1604 pas16= [HW,SCSI]
1605 See header of drivers/scsi/pas16.c.
1607 pause_on_oops=
1608 Halt all CPUs after the first oops has been printed for
1609 the specified number of seconds. This is to be used if
1610 your oopses keep scrolling off the screen.
1612 pcbit= [HW,ISDN]
1614 pcd. [PARIDE]
1615 See header of drivers/block/paride/pcd.c.
1616 See also Documentation/paride.txt.
1618 pci=option[,option...] [PCI] various PCI subsystem options:
1619 off [X86] don't probe for the PCI bus
1620 bios [X86-32] force use of PCI BIOS, don't access
1621 the hardware directly. Use this if your machine
1622 has a non-standard PCI host bridge.
1623 nobios [X86-32] disallow use of PCI BIOS, only direct
1624 hardware access methods are allowed. Use this
1625 if you experience crashes upon bootup and you
1626 suspect they are caused by the BIOS.
1627 conf1 [X86] Force use of PCI Configuration
1628 Mechanism 1.
1629 conf2 [X86] Force use of PCI Configuration
1630 Mechanism 2.
1631 noaer [PCIE] If the PCIEAER kernel config parameter is
1632 enabled, this kernel boot option can be used to
1633 disable the use of PCIE advanced error reporting.
1634 nodomains [PCI] Disable support for multiple PCI
1635 root domains (aka PCI segments, in ACPI-speak).
1636 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1637 Configuration
1638 nomsi [MSI] If the PCI_MSI kernel config parameter is
1639 enabled, this kernel boot option can be used to
1640 disable the use of MSI interrupts system-wide.
1641 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1642 routing table. These calls are known to be buggy
1643 on several machines and they hang the machine
1644 when used, but on other computers it's the only
1645 way to get the interrupt routing table. Try
1646 this option if the kernel is unable to allocate
1647 IRQs or discover secondary PCI buses on your
1648 motherboard.
1649 rom [X86] Assign address space to expansion ROMs.
1650 Use with caution as certain devices share
1651 address decoders between ROMs and other
1652 resources.
1653 norom [X86] Do not assign address space to
1654 expansion ROMs that do not already have
1655 BIOS assigned address ranges.
1656 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1657 assigned automatically to PCI devices. You can
1658 make the kernel exclude IRQs of your ISA cards
1659 this way.
1660 pirqaddr=0xAAAAA [X86] Specify the physical address
1661 of the PIRQ table (normally generated
1662 by the BIOS) if it is outside the
1663 F0000h-100000h range.
1664 lastbus=N [X86] Scan all buses thru bus #N. Can be
1665 useful if the kernel is unable to find your
1666 secondary buses and you want to tell it
1667 explicitly which ones they are.
1668 assign-busses [X86] Always assign all PCI bus
1669 numbers ourselves, overriding
1670 whatever the firmware may have done.
1671 usepirqmask [X86] Honor the possible IRQ mask stored
1672 in the BIOS $PIR table. This is needed on
1673 some systems with broken BIOSes, notably
1674 some HP Pavilion N5400 and Omnibook XE3
1675 notebooks. This will have no effect if ACPI
1676 IRQ routing is enabled.
1677 noacpi [X86] Do not use ACPI for IRQ routing
1678 or for PCI scanning.
1679 use_crs [X86] Use _CRS for PCI resource
1680 allocation.
1681 routeirq Do IRQ routing for all PCI devices.
1682 This is normally done in pci_enable_device(),
1683 so this option is a temporary workaround
1684 for broken drivers that don't call it.
1685 skip_isa_align [X86] do not align io start addr, so can
1686 handle more pci cards
1687 firmware [ARM] Do not re-enumerate the bus but instead
1688 just use the configuration from the
1689 bootloader. This is currently used on
1690 IXP2000 systems where the bus has to be
1691 configured a certain way for adjunct CPUs.
1692 noearly [X86] Don't do any early type 1 scanning.
1693 This might help on some broken boards which
1694 machine check when some devices' config space
1695 is read. But various workarounds are disabled
1696 and some IOMMU drivers will not work.
1697 bfsort Sort PCI devices into breadth-first order.
1698 This sorting is done to get a device
1699 order compatible with older (<= 2.4) kernels.
1700 nobfsort Don't sort PCI devices into breadth-first order.
1701 cbiosize=nn[KMG] The fixed amount of bus space which is
1702 reserved for the CardBus bridge's IO window.
1703 The default value is 256 bytes.
1704 cbmemsize=nn[KMG] The fixed amount of bus space which is
1705 reserved for the CardBus bridge's memory
1706 window. The default value is 64 megabytes.
1708 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1709 Management.
1710 off Disable ASPM.
1711 force Enable ASPM even on devices that claim not to support it.
1712 WARNING: Forcing ASPM on may cause system lockups.
1714 pcmv= [HW,PCMCIA] BadgePAD 4
1716 pd. [PARIDE]
1717 See Documentation/paride.txt.
1719 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1720 boot time.
1721 Format: { 0 | 1 }
1722 See arch/parisc/kernel/pdc_chassis.c
1724 pf. [PARIDE]
1725 See Documentation/paride.txt.
1727 pg. [PARIDE]
1728 See Documentation/paride.txt.
1730 pirq= [SMP,APIC] Manual mp-table setup
1731 See Documentation/i386/IO-APIC.txt.
1733 plip= [PPT,NET] Parallel port network link
1734 Format: { parport<nr> | timid | 0 }
1735 See also Documentation/parport.txt.
1737 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1738 Override pmtimer IOPort with a hex value.
1739 e.g. pmtmr=0x508
1741 pnp.debug [PNP]
1742 Enable PNP debug messages. This depends on the
1743 CONFIG_PNP_DEBUG_MESSAGES option.
1745 pnpacpi= [ACPI]
1746 { off }
1748 pnpbios= [ISAPNP]
1749 { on | off | curr | res | no-curr | no-res }
1751 pnp_reserve_irq=
1752 [ISAPNP] Exclude IRQs for the autoconfiguration
1754 pnp_reserve_dma=
1755 [ISAPNP] Exclude DMAs for the autoconfiguration
1757 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1758 Ranges are in pairs (I/O port base and size).
1760 pnp_reserve_mem=
1761 [ISAPNP] Exclude memory regions for the
1762 autoconfiguration.
1763 Ranges are in pairs (memory base and size).
1765 dynamic_printk
1766 Enables pr_debug()/dev_dbg() calls if
1767 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
1768 be switched on/off via <debugfs>/dynamic_printk/modules
1770 print-fatal-signals=
1771 [KNL] debug: print fatal signals
1772 print-fatal-signals=1: print segfault info to
1773 the kernel console.
1774 default: off.
1776 printk.time= Show timing data prefixed to each printk message line
1777 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1779 profile= [KNL] Enable kernel profiling via /proc/profile
1780 Format: [schedule,]<number>
1781 Param: "schedule" - profile schedule points.
1782 Param: <number> - step/bucket size as a power of 2 for
1783 statistical time based profiling.
1784 Param: "sleep" - profile D-state sleeping (millisecs).
1785 Requires CONFIG_SCHEDSTATS
1786 Param: "kvm" - profile VM exits.
1788 processor.max_cstate= [HW,ACPI]
1789 Limit processor to maximum C-state
1790 max_cstate=9 overrides any DMI blacklist limit.
1792 processor.nocst [HW,ACPI]
1793 Ignore the _CST method to determine C-states,
1794 instead using the legacy FADT method
1796 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1797 before loading.
1798 See Documentation/ramdisk.txt.
1800 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1801 probe for; one of (bare|imps|exps|lifebook|any).
1802 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1803 per second.
1804 psmouse.resetafter= [HW,MOUSE]
1805 Try to reset the device after so many bad packets
1806 (0 = never).
1807 psmouse.resolution=
1808 [HW,MOUSE] Set desired mouse resolution, in dpi.
1809 psmouse.smartscroll=
1810 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1811 0 = disabled, 1 = enabled (default).
1813 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1814 Format:
1815 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1817 pt. [PARIDE]
1818 See Documentation/paride.txt.
1820 pty.legacy_count=
1821 [KNL] Number of legacy pty's. Overwrites compiled-in
1822 default number.
1824 quiet [KNL] Disable most log messages
1826 r128= [HW,DRM]
1828 raid= [HW,RAID]
1829 See Documentation/md.txt.
1831 ramdisk_blocksize= [RAM]
1832 See Documentation/ramdisk.txt.
1834 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1835 See Documentation/ramdisk.txt.
1837 rcupdate.blimit= [KNL,BOOT]
1838 Set maximum number of finished RCU callbacks to process
1839 in one batch.
1841 rcupdate.qhimark= [KNL,BOOT]
1842 Set threshold of queued
1843 RCU callbacks over which batch limiting is disabled.
1845 rcupdate.qlowmark= [KNL,BOOT]
1846 Set threshold of queued RCU callbacks below which
1847 batch limiting is re-enabled.
1849 rdinit= [KNL]
1850 Format: <full_path>
1851 Run specified binary instead of /init from the ramdisk,
1852 used for early userspace startup. See initrd.
1854 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1855 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1856 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1858 relax_domain_level=
1859 [KNL, SMP] Set scheduler's default relax_domain_level.
1860 See Documentation/cpusets.txt.
1862 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1864 reservetop= [X86-32]
1865 Format: nn[KMG]
1866 Reserves a hole at the top of the kernel virtual
1867 address space.
1869 reset_devices [KNL] Force drivers to reset the underlying device
1870 during initialization.
1872 resume= [SWSUSP]
1873 Specify the partition device for software suspend
1875 resume_offset= [SWSUSP]
1876 Specify the offset from the beginning of the partition
1877 given by "resume=" at which the swap header is located,
1878 in <PAGE_SIZE> units (needed only for swap files).
1879 See Documentation/power/swsusp-and-swap-files.txt
1881 retain_initrd [RAM] Keep initrd memory after extraction
1883 rhash_entries= [KNL,NET]
1884 Set number of hash buckets for route cache
1886 riscom8= [HW,SERIAL]
1887 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1889 ro [KNL] Mount root device read-only on boot
1891 root= [KNL] Root filesystem
1893 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1894 mount the root filesystem
1896 rootflags= [KNL] Set root filesystem mount option string
1898 rootfstype= [KNL] Set root filesystem type
1900 rootwait [KNL] Wait (indefinitely) for root device to show up.
1901 Useful for devices that are detected asynchronously
1902 (e.g. USB and MMC devices).
1904 root_plug.vendor_id=
1905 [ROOTPLUG] Override the default vendor ID
1907 root_plug.product_id=
1908 [ROOTPLUG] Override the default product ID
1910 root_plug.debug=
1911 [ROOTPLUG] Enable debugging output
1913 rw [KNL] Mount root device read-write on boot
1915 S [KNL] Run init in single mode
1917 sa1100ir [NET]
1918 See drivers/net/irda/sa1100_ir.c.
1920 sbni= [NET] Granch SBNI12 leased line adapter
1922 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1923 Format: <io>[,<timeout>[,<isapnp>]]
1925 scsi_debug_*= [SCSI]
1926 See drivers/scsi/scsi_debug.c.
1928 scsi_default_dev_flags=
1929 [SCSI] SCSI default device flags
1930 Format: <integer>
1932 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1933 Format: <vendor>:<model>:<flags>
1934 (flags are integer value)
1936 scsi_logging_level= [SCSI] a bit mask of logging levels
1937 See drivers/scsi/scsi_logging.h for bits. Also
1938 settable via sysctl at dev.scsi.logging_level
1939 (/proc/sys/dev/scsi/logging_level).
1940 There is also a nice 'scsi_logging_level' script in the
1941 S390-tools package, available for download at
1942 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1944 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1945 discovered. async scans them in kernel threads,
1946 allowing boot to proceed. none ignores them, expecting
1947 user space to do the scan.
1949 selinux [SELINUX] Disable or enable SELinux at boot time.
1950 Format: { "0" | "1" }
1951 See security/selinux/Kconfig help text.
1952 0 -- disable.
1953 1 -- enable.
1954 Default value is set via kernel config option.
1955 If enabled at boot time, /selinux/disable can be used
1956 later to disable prior to initial policy load.
1958 selinux_compat_net =
1959 [SELINUX] Set initial selinux_compat_net flag value.
1960 Format: { "0" | "1" }
1961 0 -- use new secmark-based packet controls
1962 1 -- use legacy packet controls
1963 Default value is 0 (preferred).
1964 Value can be changed at runtime via
1965 /selinux/compat_net.
1967 serialnumber [BUGS=X86-32]
1969 shapers= [NET]
1970 Maximal number of shapers.
1972 show_msr= [x86] show boot-time MSR settings
1973 Format: { <integer> }
1974 Show boot-time (BIOS-initialized) MSR settings.
1975 The parameter means the number of CPUs to show,
1976 for example 1 means boot CPU only.
1978 sim710= [SCSI,HW]
1979 See header of drivers/scsi/sim710.c.
1981 simeth= [IA-64]
1982 simscsi=
1984 slram= [HW,MTD]
1986 slub_debug[=options[,slabs]] [MM, SLUB]
1987 Enabling slub_debug allows one to determine the
1988 culprit if slab objects become corrupted. Enabling
1989 slub_debug can create guard zones around objects and
1990 may poison objects when not in use. Also tracks the
1991 last alloc / free. For more information see
1992 Documentation/vm/slub.txt.
1994 slub_max_order= [MM, SLUB]
1995 Determines the maximum allowed order for slabs.
1996 A high setting may cause OOMs due to memory
1997 fragmentation. For more information see
1998 Documentation/vm/slub.txt.
2000 slub_min_objects= [MM, SLUB]
2001 The minimum number of objects per slab. SLUB will
2002 increase the slab order up to slub_max_order to
2003 generate a sufficiently large slab able to contain
2004 the number of objects indicated. The higher the number
2005 of objects the smaller the overhead of tracking slabs
2006 and the less frequently locks need to be acquired.
2007 For more information see Documentation/vm/slub.txt.
2009 slub_min_order= [MM, SLUB]
2010 Determines the mininum page order for slabs. Must be
2011 lower than slub_max_order.
2012 For more information see Documentation/vm/slub.txt.
2014 slub_nomerge [MM, SLUB]
2015 Disable merging of slabs with similar size. May be
2016 necessary if there is some reason to distinguish
2017 allocs to different slabs. Debug options disable
2018 merging on their own.
2019 For more information see Documentation/vm/slub.txt.
2021 smart2= [HW]
2022 Format: <io1>[,<io2>[,...,<io8>]]
2024 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2025 attempt to substitute SMP alternatives once at boot.
2027 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2028 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2029 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2030 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2031 smsc-ircc2.ircc_irq= [HW] IRQ line
2032 smsc-ircc2.ircc_dma= [HW] DMA channel
2033 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2034 0: Toshiba Satellite 1800 (GP data pin select)
2035 1: Fast pin select (default)
2036 2: ATC IRMode
2038 snd-ad1816a= [HW,ALSA]
2040 snd-ad1848= [HW,ALSA]
2042 snd-ali5451= [HW,ALSA]
2044 snd-als100= [HW,ALSA]
2046 snd-als4000= [HW,ALSA]
2048 snd-azt2320= [HW,ALSA]
2050 snd-cmi8330= [HW,ALSA]
2052 snd-cmipci= [HW,ALSA]
2054 snd-cs4231= [HW,ALSA]
2056 snd-cs4232= [HW,ALSA]
2058 snd-cs4236= [HW,ALSA]
2060 snd-cs4281= [HW,ALSA]
2062 snd-cs46xx= [HW,ALSA]
2064 snd-dt019x= [HW,ALSA]
2066 snd-dummy= [HW,ALSA]
2068 snd-emu10k1= [HW,ALSA]
2070 snd-ens1370= [HW,ALSA]
2072 snd-ens1371= [HW,ALSA]
2074 snd-es968= [HW,ALSA]
2076 snd-es1688= [HW,ALSA]
2078 snd-es18xx= [HW,ALSA]
2080 snd-es1938= [HW,ALSA]
2082 snd-es1968= [HW,ALSA]
2084 snd-fm801= [HW,ALSA]
2086 snd-gusclassic= [HW,ALSA]
2088 snd-gusextreme= [HW,ALSA]
2090 snd-gusmax= [HW,ALSA]
2092 snd-hdsp= [HW,ALSA]
2094 snd-ice1712= [HW,ALSA]
2096 snd-intel8x0= [HW,ALSA]
2098 snd-interwave= [HW,ALSA]
2100 snd-interwave-stb=
2101 [HW,ALSA]
2103 snd-korg1212= [HW,ALSA]
2105 snd-maestro3= [HW,ALSA]
2107 snd-mpu401= [HW,ALSA]
2109 snd-mtpav= [HW,ALSA]
2111 snd-nm256= [HW,ALSA]
2113 snd-opl3sa2= [HW,ALSA]
2115 snd-opti92x-ad1848=
2116 [HW,ALSA]
2118 snd-opti92x-cs4231=
2119 [HW,ALSA]
2121 snd-opti93x= [HW,ALSA]
2123 snd-pmac= [HW,ALSA]
2125 snd-rme32= [HW,ALSA]
2127 snd-rme96= [HW,ALSA]
2129 snd-rme9652= [HW,ALSA]
2131 snd-sb8= [HW,ALSA]
2133 snd-sb16= [HW,ALSA]
2135 snd-sbawe= [HW,ALSA]
2137 snd-serial= [HW,ALSA]
2139 snd-sgalaxy= [HW,ALSA]
2141 snd-sonicvibes= [HW,ALSA]
2143 snd-sun-amd7930=
2144 [HW,ALSA]
2146 snd-sun-cs4231= [HW,ALSA]
2148 snd-trident= [HW,ALSA]
2150 snd-usb-audio= [HW,ALSA,USB]
2152 snd-via82xx= [HW,ALSA]
2154 snd-virmidi= [HW,ALSA]
2156 snd-wavefront= [HW,ALSA]
2158 snd-ymfpci= [HW,ALSA]
2160 softlockup_panic=
2161 [KNL] Should the soft-lockup detector generate panics.
2163 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2164 See Documentation/sonypi.txt
2166 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2167 See Documentation/specialix.txt.
2169 spia_io_base= [HW,MTD]
2170 spia_fio_base=
2171 spia_pedr=
2172 spia_peddr=
2174 sscape= [HW,OSS]
2175 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2177 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2178 See Documentation/scsi/st.txt.
2180 sti= [PARISC,HW]
2181 Format: <num>
2182 Set the STI (builtin display/keyboard on the HP-PARISC
2183 machines) console (graphic card) which should be used
2184 as the initial boot-console.
2185 See also comment in drivers/video/console/sticore.c.
2187 sti_font= [HW]
2188 See comment in drivers/video/console/sticore.c.
2190 stifb= [HW]
2191 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2193 sunrpc.pool_mode=
2194 [NFS]
2195 Control how the NFS server code allocates CPUs to
2196 service thread pools. Depending on how many NICs
2197 you have and where their interrupts are bound, this
2198 option will affect which CPUs will do NFS serving.
2199 Note: this parameter cannot be changed while the
2200 NFS server is running.
2202 auto the server chooses an appropriate mode
2203 automatically using heuristics
2204 global a single global pool contains all CPUs
2205 percpu one pool for each CPU
2206 pernode one pool for each NUMA node (equivalent
2207 to global on non-NUMA machines)
2209 swiotlb= [IA-64] Number of I/O TLB slabs
2211 switches= [HW,M68k]
2213 sym53c416= [HW,SCSI]
2214 See header of drivers/scsi/sym53c416.c.
2216 sysrq_always_enabled
2217 [KNL]
2218 Ignore sysrq setting - this boot parameter will
2219 neutralize any effect of /proc/sys/kernel/sysrq.
2220 Useful for debugging.
2222 t128= [HW,SCSI]
2223 See header of drivers/scsi/t128.c.
2225 tdfx= [HW,DRM]
2227 test_suspend= [SUSPEND]
2228 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2229 standby suspend) as the system sleep state to briefly
2230 enter during system startup. The system is woken from
2231 this state using a wakeup-capable RTC alarm.
2233 thash_entries= [KNL,NET]
2234 Set number of hash buckets for TCP connection
2236 thermal.act= [HW,ACPI]
2237 -1: disable all active trip points in all thermal zones
2238 <degrees C>: override all lowest active trip points
2240 thermal.crt= [HW,ACPI]
2241 -1: disable all critical trip points in all thermal zones
2242 <degrees C>: override all critical trip points
2244 thermal.nocrt= [HW,ACPI]
2245 Set to disable actions on ACPI thermal zone
2246 critical and hot trip points.
2248 thermal.off= [HW,ACPI]
2249 1: disable ACPI thermal control
2251 thermal.psv= [HW,ACPI]
2252 -1: disable all passive trip points
2253 <degrees C>: override all passive trip points to this value
2255 thermal.tzp= [HW,ACPI]
2256 Specify global default ACPI thermal zone polling rate
2257 <deci-seconds>: poll all this frequency
2258 0: no polling (default)
2260 tmscsim= [HW,SCSI]
2261 See comment before function dc390_setup() in
2262 drivers/scsi/tmscsim.c.
2264 tp720= [HW,PS2]
2266 trix= [HW,OSS] MediaTrix AudioTrix Pro
2267 Format:
2268 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2270 turbografx.map[2|3]= [HW,JOY]
2271 TurboGraFX parallel port interface
2272 Format:
2273 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2274 See also Documentation/input/joystick-parport.txt
2276 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2277 See header of drivers/scsi/u14-34f.c.
2279 uart401= [HW,OSS]
2280 Format: <io>,<irq>
2282 uart6850= [HW,OSS]
2283 Format: <io>,<irq>
2285 uhci-hcd.ignore_oc=
2286 [USB] Ignore overcurrent events (default N).
2287 Some badly-designed motherboards generate lots of
2288 bogus events, for ports that aren't wired to
2289 anything. Set this parameter to avoid log spamming.
2290 Note that genuine overcurrent events won't be
2291 reported either.
2293 unknown_nmi_panic
2294 [X86-32,X86-64]
2295 Set unknown_nmi_panic=1 early on boot.
2297 usbcore.autosuspend=
2298 [USB] The autosuspend time delay (in seconds) used
2299 for newly-detected USB devices (default 2). This
2300 is the time required before an idle device will be
2301 autosuspended. Devices for which the delay is set
2302 to a negative value won't be autosuspended at all.
2304 usbcore.usbfs_snoop=
2305 [USB] Set to log all usbfs traffic (default 0 = off).
2307 usbcore.blinkenlights=
2308 [USB] Set to cycle leds on hubs (default 0 = off).
2310 usbcore.old_scheme_first=
2311 [USB] Start with the old device initialization
2312 scheme (default 0 = off).
2314 usbcore.use_both_schemes=
2315 [USB] Try the other device initialization scheme
2316 if the first one fails (default 1 = enabled).
2318 usbcore.initial_descriptor_timeout=
2319 [USB] Specifies timeout for the initial 64-byte
2320 USB_REQ_GET_DESCRIPTOR request in milliseconds
2321 (default 5000 = 5.0 seconds).
2323 usbhid.mousepoll=
2324 [USBHID] The interval which mice are to be polled at.
2326 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2327 kernel's map of available physical RAM.
2329 vdso= [X86-32,SH,x86-64]
2330 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2331 vdso=1: enable VDSO (default)
2332 vdso=0: disable VDSO mapping
2334 vdso32= [X86-32,X86-64]
2335 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2336 vdso32=1: enable 32-bit VDSO (default)
2337 vdso32=0: disable 32-bit VDSO mapping
2339 vector= [IA-64,SMP]
2340 vector=percpu: enable percpu vector domain
2342 video= [FB] Frame buffer configuration
2343 See Documentation/fb/modedb.txt.
2345 vga= [BOOT,X86-32] Select a particular video mode
2346 See Documentation/i386/boot.txt and
2347 Documentation/svga.txt.
2348 Use vga=ask for menu.
2349 This is actually a boot loader parameter; the value is
2350 passed to the kernel using a special protocol.
2352 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2353 size of <nn>. This can be used to increase the
2354 minimum size (128MB on x86). It can also be used to
2355 decrease the size and leave more room for directly
2356 mapped kernel RAM.
2358 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2359 Format: <command>
2361 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2362 Format: <command>
2364 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2365 Format: <command>
2367 waveartist= [HW,OSS]
2368 Format: <io>,<irq>,<dma>,<dma2>
2370 wd33c93= [HW,SCSI]
2371 See header of drivers/scsi/wd33c93.c.
2373 wd7000= [HW,SCSI]
2374 See header of drivers/scsi/wd7000.c.
2376 wdt= [WDT] Watchdog
2377 See Documentation/watchdog/wdt.txt.
2379 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2380 xd_geo= See header of drivers/block/xd.c.
2382 xirc2ps_cs= [NET,PCMCIA]
2383 Format:
2384 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2386 norandmaps Don't use address space randomization
2387 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2389 ______________________________________________________________________
2391 TODO:
2393 Add documentation for ALSA options.
2394 Add more DRM drivers.